My recent travels have led to a bit of a build-up in the pile of interesting articles that I’d like to read and possibly share, so I have decided that it’s time for another round-up of the articles that are awaiting my attention, in the hope that some might be of interest to others as well … so this is the first of a two-part post in which I’m going to share the ten most interesting-looking articles on my reading pile right now…
1. A wider pelvis does not increase locomotor cost in humans, with implications for the evolution of childbirth
OK, I have to be honest. I like the look of this one A LOT, but I realise that hip abductor mechanics might not be everyone’s cup of tea! I have always felt uncomfortable with the received view about the so-called ‘obstetric dilemma’ which says that women experience pain and difficulty during childbirth as a consequence of the way our bodies have evolved to accommodate a trade-off between having large-brained babies and a need to walk long distances, and a quick glance at the abstract has shown me that the authors of this paper have at least seen reason to reconsider that view. Here’s the abstract:
“The shape of the human female pelvis is thought to reflect an evolutionary trade-off between two competing demands: a pelvis wide enough to permit the birth of large-brained infants, and narrow enough for efficient bipedal locomotion. This trade-off, known as the obstetrical dilemma, is invoked to explain the relative difficulty of human childbirth and differences in locomotor performance between men and women. The basis for the obstetrical dilemma is a standard static biomechanical model that predicts wider pelves in females increase the metabolic cost of locomotion by decreasing the effective mechanical advantage of the hip abductor muscles for pelvic stabilization during the single-leg support phase of walking and running, requiring these muscles to produce more force. Here we experimentally test this model against a more accurate dynamic model of hip abductor mechanics in men and women. The results show that pelvic width does not predict hip abductor mechanics or locomotor cost in either women or men, and that women and men are equally efficient at both walking and running. Since a wider birth canal does not increase a woman’s locomotor cost, and because selection for successful birthing must be strong, other factors affecting maternal pelvic and fetal size should be investigated in order to help explain the prevalence of birth complications caused by a neonate too large to fit through the birth canal.”
It’s freely available online and I can’t wait to read more. In fact, I’m packing it to read on my upcoming flight to Australia!
Warrener AG, Lewton KL, Pontzer H et al (2015). A wider pelvis does not increase locomotor cost in humans, with implications for the evolution of childbirth. PLOS ONE 10(3): e0118903.
2. Small-for-gestational age and large-for-gestational age thresholds to predict infants at risk of adverse delivery and neonatal outcomes: are current charts adequate? An observational study from the Born in Bradford cohort
The very short answer to this rather long title, at least from the abstract, appears to be ‘no’. The authors looked at 3980 White British and 4448 Pakistani infants with complete data for gestational age, birth weight, ethnicity, maternal height, weight and parity, and compare the prediction of adverse outcomes using an ethnic-specific chart that they constructed with the clinically recommended UK-WHO and customised birth weight charts using cut-offs for small-for-gestational age (SGA: birth weight <10th centile) and large-for-gestational age (LGA: birth weight >90th centile).
They concluded that, “Despite being recommended in national clinical guidelines, the UK-WHO and customised birth weight charts perform poorly at identifying infants at risk of adverse neonatal outcomes. Being small or large may increase the risk of an adverse outcome; however, size alone is not sensitive or specific enough with current detection to be useful. However, a significant amount of missing data for some of the outcomes may have limited the power needed to determine true associations.”
I’ve spent several years ranting about the futility of using population-level standards against which to measure individuals, although I understand why those who run systems of care find such notions attractive, so I’m interested to look at this in more depth and see if and how there are other areas in which the ethnic-specific charts are different.
Norris T, Johnson W, Farrar D et al (2015). Small-for-gestational age and large-for-gestational age thresholds to predict infants at risk of adverse delivery and neonatal outcomes: are current charts adequate? An observational study from the Born in Bradford cohort. BMJ Open 2015;5:e006743 doi:10.1136/bmjopen-2014-006743
3. Vegan–vegetarian diets in pregnancy: danger or panacea? A systematic narrative review
The authors of this paper noted that, although vegan–vegetarian diets are increasingly popular, no recent systematic reviews on vegan–vegetarian diets in pregnancy exist … so they reviewed the literature for us. They focused on healthy pregnant women and found 22 full-text papers which met their inclusion criteria, but the papers were so heterogenous (or different from each other) that they were only able to complete a narrative review.
“None of the studies reported an increase in severe adverse outcomes or in major malformations, except one report of increased hypospadias in infants of vegetarian mothers. Five studies reported vegetarian mothers had lower birthweight babies, yet two studies reported higher birthweights. The duration of pregnancy was available in six studies and was similar between vegan–vegetarians and omnivores. The nine heterogeneous studies on microelements and vitamins suggest vegan–vegetarian women may be at risk of vitamin B12 and iron deficiencies.”
The conclusion of this paper is that, “the evidence on vegan–vegetarian diets in pregnancy is heterogeneous and scant. The lack of randomised studies prevents us from distinguishing the effects of diet from confounding factors. Within these limits, vegan–vegetarian diets may be considered safe in pregnancy, provided that attention is paid to vitamin and trace element requirements.”
Piccoli GB, Clari R, Vigotti et al (2015). Vegan–vegetarian diets in pregnancy: danger or panacea? A systematic narrative review. BJOG: An International Journal of Obstetrics & Gynaecology 122(5): 623-33. DOI: 10.1111/1471-0528.13280
4. “My midwife said that having a glass of red wine was actually better for the baby”: a focus group study of women and their partner’s knowledge and experiences relating to alcohol consumption in pregnancy
No prizes for guessing why I’m interested to read this paper; the rather controversial title has done its job of getting my attention! These researchers ran focus groups with pregnant women, newly delivered mothers and their partners – a total of 21 participants – and aimed to explore participant’s knowledge about the effects of alcohol consumption during pregnancy, their sources of information on this issue, and the psycho-social influences on their drinking behaviour.
“The findings indicated that although the majority of participants knew not to drink alcohol in pregnancy they had limited information on the specific harmful effects. In addition, routine enquiry and the provision of information by health care professionals were seen as lacking”
The researchers recommendations include that, “Firstly, public health messages and educational materials need to provide clear and consistent information about the effects of alcohol consumption on the developing baby. Additionally, more thorough and consistent routine enquiry for alcohol consumption in pregnant women needs to occur. Finally, it is important to ensure ongoing education for health professionals on the issue of alcohol consumption during pregnancy.”
Crawford-Williams F, Steen M, Esterman A et al (2015) “My midwife said that having a glass of red wine was actually better for the baby”: a focus group study of women and their partner’s knowledge and experiences relating to alcohol consumption in pregnancy. BMC Pregnancy and Childbirth 2015, 15:79 doi:10.1186/s12884-015-0506-3
5. Influence of Acupuncture on the Third Stage of Labor: A Randomized Controlled Trial
I’m curious about this one too. It is a small randomised controlled trial of 76 women who had a normal spontaneous birth and who were then randomly assigned to receive true acupuncture or placebo acupuncture (also known as sham acupuncture). The authors say that the management of the third stage of labor was the same in both groups, though I’ve not yet dug into the study to find out what that ‘management’ constituted.
The authors report that they found statistically significant differences between the two groups, “with an average time to placental expulsion of 15.2 minutes in the placebo group and 5.2 minutes in the acupuncture group. No major complications occurred in either group.”
If I’m honest, I’m skeptical that we need to routinely interfere with the birth of the placenta – though I’m a big fan of treatment if a woman bleeds excessively, of course – but, as this is a key interest of mine, I’m always keen to read new and interesting papers in this area.
López-Garrido B, García-Gonzalo J,Patrón-Rodriguez C et al (2015). Influence of Acupuncture on the Third Stage of Labor: A Randomized Controlled Trial. Journal of Midwifery & Women’s Health 60(2): 199-205.
I hope some of these will interest you too … five more coming up very soon!